A positive temperature coefficient (PTC) element exhibits a PTC effect that renders the same to be useful as a circuit protection device, such as a resettable fuse. The PTC element includes a PTC polymer material and first and second electrodes attached to two opposite surfaces of PTC polymer material.
The PTC polymer material includes a polymer matrix that contains a crystalline region and a non-crystalline region, and a particulate conductive filler dispersed in the non-crystalline region of the polymer matrix and formed into a continuous conductive path for electrical conduction between the first and second electrodes. The PTC effect is referred to as a phenomenon that when the temperature of the polymer matrix is raised to its melting point, crystals in the crystalline region start to melt, which results in generation of a new non-crystalline region. As the new non-crystalline region is increased to an extent to merge into the original non-crystalline region, the conductive path of the particulate conductive filler will become discontinuous and the resistance of the PTC polymer material will sharply increase, thereby resulting in electrical disconnection between the first and second electrodes.
Although the conductivity of the PTC polymer material can be considerably increased by using the particulate non-carbonaceous particles, such as metal powders, such conductive non-carbonaceous particles having high conductivity tend to result in undesired electric arc generated within the PTC polymer material during use.
The electric arc thus formed could deteriorate the molecular structure of the polymer matrix of the PTC polymer material and result in unstable electrical property of the PTC element and reduction in service life of the PTC element.
U.S. Pat. No. 8,508,327B2 discloses a PTC polymer material. The PTC polymer material includes a polymer matrix and titanium carbide particles dispersed in the polymer matrix. The titanium carbide particles have a residual oxygen content greater than 0.3 wt % based on a total weight of the titanium carbide particles, so that electrical stability of the PTC polymer material may be improved. However, there is still a need to improve the electrical stability of the PTC polymer material.